The invention relates to an equalising gear for a wind energy system comprising a gear unit having three in- or outputs, an input being connected to the rotor of the wind energy system, the first output being connected to a generator and the second output being connected to the input shaft of a continuously controllable gearing, the output shaft of which is connected to the generator-side output of the gear unit.
The invention further relates to a method for changing or switching the power range of an equalising gear of a wind energy system when the wind strength changes comprising a gear unit having three in- or outputs, an input being connected to the rotor of the wind energy system, the first output being connected to a generator and the second output being connected to the input shaft of a continuously controllable gearing.
State of the art wind energy systems generally function at variable rotor speeds and have active torque control of the transmission for regulation purposes. This is because the variable rotational speed of the rotor, on account of the moment of inertia thereof, dampens changes in the rotational speed of the transmission, thus enabling the rotor blade adjustment system to be optimally configured. Furthermore, torque control of the transmission enables the loads on the system to be reduced and the quality of the energy supplied to the grid to be optimised. The improved aerodynamic efficiency in the part-load range is a further advantage of the variable rotor speed.
The variable rotational speed of the generator, and the associated superimposed acceleration torque, generally has a detrimental impact on the gear unit in particular, which must be made stronger as a result. A further drawback is that the inputs with variable rotational speeds that are predominantly used in the prior art generally function using frequency converters, which can only generate power of the required quality by using considerably more expensive technology.
WO 2004/088132 A discloses a device which avoids the aforementioned drawbacks by using an equalising gear and a hydrodynamic torque converter. However, a disadvantage of this solution is the considerable cost of the gear and the hydrodynamic system which must be configured for relatively high power levels. In particular, the high levels of hydraulic loss associated with this device are particularly acute in large rotational speed ranges, thus causing high losses in the part-load range of the system and high start-up costs.
These drawbacks are largely avoided by the gear known from WO 2004/109157 A. In this case, a hydraulic system is used which keeps the power directed via the hydraulic system at a relatively low level in the part-load range by means of a multi-path equalising gear. However, the complicated multi-path equalising gear, in conjunction with a complex coupling system and pumps which can only be adjusted with considerable effort and are both operated at variable rotational speeds, is a major drawback of this solution.